Environmental Science - Wind

Renewable Energy
Wind

Abstract We have been harnessing the wind’s energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water and grinding grain. Today, the windmill’s modern equivalent, a wind turbine, can use the wind’s energy to generate electricity. Wind turbines can be used as stand-alone applications, such as for pumping water or to help reduce homeowners’ electric bills, or they can be connected to a utility power grid to supply electricity to a community. Wind energy is a converted form of solar energy. The sun’s radiation heats different parts of the earth at different rates, which is easy to notice during the day and night. This is also evident when different surfaces, such as water and land, absorb or reflect heat at different rates. This causes portions of the atmosphere to warm differently. Hot air rises, reducing the atmospheric pressure at the earth’s surface, and cooler air is drawn in to replace it, resulting in wind (www.awea.org). Wind is transformed from kinetic energy into mechanical or electrical energy that can be harnessed for practical use. Mechanical energy is most commonly used for pumping water in rural or remote locations. Predominately, windmills located on farms are used to pump water to crops and livestock (Frank, 1991).
There are two basic designs of wind electric turbines, vertical-axis, sometimes referred to as egg-beater style and horizontal-axis or propeller style machines. Vertical-axis wind machines have blades that go from top to bottom. The most common type, the Darrieus wind turbine, was named after the French engineer Georges Darrieus who patented the design in 1931. This type of vertical wind machine typically stands 100 feet tall and 50 feet wide. Vertical-axis wind machines make up only a very small share of the wind machines used today. Most wind machines being used today are the horizontal-axis type. Horizontal-axis wind machines have blades like airplane propellers. A typical horizontal wind machine stands as tall as a 20-story building and has three blades that span 200 feet across, the size of these depend greatly on the location, off-shore turbines tend to be larger than those on-shore (Secrest, 1994). Generated electricity of wind turbines is measured in watts. Watts are very small units so the terms kilowatt (kW = 1,000 watts), megawatts (MW = 1 million watts), and gigawatt (GW = 1 billion watts) are commonly used to describe the capacity of generating units like wind units or other power plants. Electricity production and consumption are most commonly measured in kilowatt-hours (kWh). A kilowatt-hour means one kilowatt of electricity produced or consumed, regardless of the amount of actual time it takes to produce or consume the kilowatt of electricity. A megawatt of wind energy is enough to supply between 225 – 300 households (www.awea.org). Wind energy offers many advantages explaining why it is the fastest growing energy source in the world. Wind energy is fueled by the wind, so the fuel source is clean. It doesn’t pollute the air in the same manner as traditional power plants that use combustible fuel, such as coal, natural gas or garbage. Because wind energy is a domestic source of energy, it is used, mostly, in the countries/areas where it is harvested, making them less dependent on foreign sources of energy. Wind is an abundant renewable energy source that cannot be exhausted. Wind turbines can be built on farms which benefit the economy in rural areas. Power plant owners pay rent to the landowners for the area(s) that the turbine(s) occupy. This enables farmers the ability to continue to work/use the land because the turbines only use a small portion of the land.
The cost of wind energy can depend greatly on how much energy can be produced at a particular site and the cost of getting it from the site to where it is needed. Favorable wind sites are often located in remote locations far from where the power is needed making it necessary to build transmission lines.
According to Global Winds (Global Winds Harvest), the following factors are important for determining whether land might be part of a viable wind power project:
1. Wind Resource – as a rule of thumb, wind speeds of at least 17 miles per hour are typically required to generate sufficient power to make a wind power project economically viable.
2. Interconnection/Transmission – because the costs of transporting power to the electrical grid are high, project viability typically requires that existing transmission lines be within at least five (5) to ten (10) miles of the proposed wind farm.
3. Land Area – to avoid excessive power losses from turbulence, large wind turbines are typically spaced 1000 to 2000 feet apart. On average, this results in a total wind farm land area of approximately 60 to 100 acres per turbine.
Hillary Watts (2005) writes in High Country News:
If you think wind energy is a good alternative to fossil fuels, but you also care about wildlife, you’ve probably worried about the possible “lawnmower” effect of spinning wind turbines on birds and bats.
At least some of that concern is justified. In the mid 1980s, people reported seeing piles of dead raptors at Altamont Pass Wind Resource Area near San Francisco, one of the nation’s first wind farms. When a Sierra Club employee later described wind turbines as the “Cuisinarts of the sky,” newspapers went wild with reports of hashed-up hawks, and opponents of alternative energy seized on this new excuse to halt wind-farm development. Another alarm was set off in 2003 when it came to light that turbines at the Mountaineer Wind Energy Center in West Virginia had killed about 2,000 bats in a two-month period.
Wind turbines do kill birds and bats, but the scale of damage varies widely, depending on several factors, including the wind farm’s location, its turbine design, and the species of birds and bats that live nearby or migrate through. However, compared to many other ways that humans kill winged animals, turbine blades generally cut only a sliver out of the pie.
According to the American Wind Energy Association, wind turbines account for only one out of every 5,000 – 10,000 human-caused bird kills nationwide. Communication towers, automobiles and domestic cats account for far more bird fatalities (www.awea.org). Research is now being conducted to increase the knowledge of wind resources. This involves the testing of more and more areas for the possibility of placing wind farms where the wind is stronger and more reliable.
In conclusion, as it becomes necessary to look for innovative means to supply energy to our communities without compromising our environment, the demand for wind energy will be a viable option to develop and bring into main stream society as a predominant source of energy.
Bibliography
Frank, D. (1991, August). Blowing in the Wind. Popular Mechanics , pp. 40-43.
Secrest, R. (1994). Wind Turbine How products are made. Retrieved March 20, 2010, from Encyclodpedia.com: http://www.encyclopedia.com/doc/1G2-2896500107.html
Watts, H. (2005, May 2). Blades, Birds and Batts: Wind Energy and Wildlife Not a Cut and Dried Issue. High Country News , p. 12. www.awea.org. (n.d.). Retrieved March 3, 2010, from American Wind Energy Association: http://awea.org.faq
Global Winds Harvest. (n.d.). Global Winds Harvest. Retrieved April 4, 2010, from Global Winds Harvest: www.globalwinds.com

Bibliography: Frank, D. (1991, August). Blowing in the Wind. Popular Mechanics , pp. 40-43. Secrest, R. (1994). Wind Turbine How products are made. Retrieved March 20, 2010, from Encyclodpedia.com: http://www.encyclopedia.com/doc/1G2-2896500107.html Watts, H. (2005, May 2). Blades, Birds and Batts: Wind Energy and Wildlife Not a Cut and Dried Issue. High Country News , p. 12. www.awea.org. (n.d.). Retrieved March 3, 2010, from American Wind Energy Association: http://awea.org.faq Global Winds Harvest. (n.d.). Global Winds Harvest. Retrieved April 4, 2010, from Global Winds Harvest: www.globalwinds.com